Vessels intended to contain fluid may develop small leaks during manufacture, or at some time during their useful life. A leak may render the vessel unsuitable for its intended use. A leak may also result in unwanted pollutants entering the atmosphere. Accordingly, leak detectors and leak detection methods have been devised to detect the presence of small leaks so that the vessel may be repaired or replaced during the manufacturing process or in the field. Most commonly leaks are detected by pressurizing the vessel with a gas comprising a tracer gas, and then analyzing the ambient air at the surface of the vessel for the presence, and, in some cases, the concentration of the tracer gas.
A preferred tracer gas is helium due to its inertness, small molecular structure and high thermal conductivity which aids detection. Its small molecular structure permits it to easily pass through the smallest of leaks in a vessel and to be easily detected by instrumentation such as a mass spectrometer or thermal conductivity analyzer. However, the natural sources of helium on earth are limited, and its recovery and refinement are costly. Hence helium is costly and its conservation and recovery in repetitive leak detecting operations is well justified economically. With the recovery of helium effectuated, its use can economically be extended to other integrity testing of vessels, such as to pressure testing or pressure proving of vessels. As used herein, ascertaining the integrity of a vessel shall mean raising the pressure inside the vessel to a desired pressure thereby demonstrating that the vessel does not burst or develop a leak apparent to unaided human senses, or performing a leak detection upon the vessel using specialized equipment for the purpose of detecting leaks.